Group 2: The meaning of modulus of elasticity and fracture toughness for resin compositesKelly Griffith, Lance Gunter, Joshua Haentges, Erik Hageman, Zohra Hasham, Nellab HashimiThe modulus of elasticity is defined as the comparative stiffness of a material. A stiffer material will have a higher elastic modulus. Fracture toughness is the amount of stress required to propagate a pre-existing defect. Describes the breaking strength of a material with a pre-existing defect. These two properties will be evaluated for resin composites in our article through journal articles. Packable composites have a higher filler load and elastic modulus than flowable composites. Packaging could also reduce shrinkage. Fluids have less filler and are used as coatings and sealants. They can't handle a lot of force, but this helps relieve stress from shrinkage. However, this can be counteracted because they shrink during polymerization. The flowable and packable composite resins were tested for shear strength 30 minutes, 1 day and 1 week, after curing under constant pressure. The dimethacrylate resins tested were: Alert/- Flow It, Filtek P 60/Filtek Flow, Admira/Admira Flow, an ormocer resin, and a microfilled composite resin. The resins increased their strength within a week. Packable composites were stronger than fluids, but variable between manufacturers. Ormocer resin had a lower elastic modulus than other compactible resins. Although fluids have lower elastic modules, they contract more, so shrinkage stress may not be better than packable composites. (Helvatjoglu et al) Dr. Nuray Attar's article focused on comparing the flexural strength and elastic modulus of condensable and hybrid composite resins. The study focused on four...... half of the paper ......007 vol.21 no.1Helvatjoglu-Antoniades M, Papadogiannis Y, Lakes RS, Dionysopoulos P, andPapadogiannis D. Dynamic and Static Elastic Moduli of Packable and flowable composite resins and their development after initial photopolymerization. Dent Mater. 2006; 22:450-459. Kostantinos M, Silikas N and Watts DC. Correlation between filler content and elastic properties of resin composites. Dent Mater. 2008; 24: 932-939.Nuray, A. A comparison of the flexural strength and elastic modulus of condensable and hybrid composite resins. ARASTIRMA , 30, 42-50.Roberts JC, Powers JM and Craig RG. Fracture resistance of composite and unfilled reconstructive resins. Dent Res 1977; 56(7): 748-753.Sabbagh J, Vreven J and Leloup G. Dynamic and static modulus of elasticity of resin-based materials. Dent Mater. 2002; 18: 64-71.